Mesa Vista Observatory
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Mesa Vista Observatory clear sky chart from 2005-11-06 to 2025-04-26.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	3 4 2 4 3 4 4 4 6% 7% 59%	117528
	Night	3 4 2 4 3 3 4 3 5% 7% 62%	119984
Transparency	Day	21% 6% 10% 20% 27% 16%	117285
	Night	20% 6% 10% 20% 28% 16%	119817
Seeing	Day	10% 19% 30% 26% 12% 2	15721
	Night	6% 14% 32% 32% 15% 2	25947

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	1 7% 4 6% 2 3 3 2 5% 6% 61%	3914
	11th to 20th	Day	2 3 3 5% 2 2 3 2 3 5% 70%	4100
	21st to end	Day	2 6% 2 6% 3 4 4 3 5% 6% 59%	4510
February	1st to 10th	Day	2 6% 2 5% 4 3 3 3 5% 8% 60%	1857
	11th to 20th	Day	2 6% 2 5% 3 3 4 3 6% 7% 60%	1949
	21st to end	Day	2 8% 1 4 3 3 2 2 5% 6% 63%	1650
March	1st to 10th	Day	1 6% 2 4 3 3 3 3 5% 7% 65%	4654
	11th to 20th	Day	3 6% 2 6% 4 4 5% 4 6% 7% 53%	5000
	21st to end	Day	2 4 1 4 3 3 4 3 5% 8% 61%	5720
April	1st to 10th	Day	2 4 1 4 3 4 4 4 6% 7% 62%	2400
	11th to 20th	Day	4 5% 2 5% 3 3 3 3 5% 5% 62%	2371
	21st to end	Day	3 5% 2 4 3 3 4 3 4 7% 63%	2341
May	1st to 10th	Day	3 3 1 3 3 2 3 3 5% 5% 70%	3800
	11th to 20th	Day	7% 4 1 4 3 3 4 4 6% 7% 57%	3959
	21st to end	Day	2 1 1 2 2 2 3 3 5% 6% 74%	4825
June	1st to 10th	Day	2 2 1 4 3 3 5% 4 7% 10% 60%	2660
	11th to 20th	Day	3 2 1 3 3 3 4 3 5% 6% 68%	2660
	21st to end	Day	6% 4 1 4 4 5% 5% 4 7% 7% 53%	2660
July	1st to 10th	Day	3 3 1 4 4 5% 7% 5% 8% 9% 51%	4430
	11th to 20th	Day	2 3 1 5% 6% 8% 10% 8% 10% 10% 38%	4148
	21st to end	Day	5% 5% 2 7% 6% 7% 9% 7% 10% 9% 34%	4454
August	1st to 10th	Day	4 3 1 6% 7% 8% 8% 7% 9% 9% 40%	3939
	11th to 20th	Day	3 3 1 4 4 4 5% 5% 7% 10% 54%	3726
	21st to end	Day	4 3 2 7% 6% 6% 7% 5% 9% 10% 40%	4180
September	1st to 10th	Day	6% 4 2 6% 5% 4 5% 4 7% 7% 48%	2280
	11th to 20th	Day	7% 4 2 4 3 4 4 4 6% 8% 54%	2280
	21st to end	Day	4 2 1 3 2 3 3 4 5% 7% 66%	2083
October	1st to 10th	Day	5% 3 1 3 3 2 2 2 3 5% 71%	3170
	11th to 20th	Day	6% 4 2 5% 3 3 4 3 4 6% 62%	3150
	21st to end	Day	3 3 1 2 2 2 1 1 3 4 78%	3438
November	1st to 10th	Day	2 3 1 3 2 3 3 2 5% 7% 70%	1859
	11th to 20th	Day	2 3 1 3 2 3 3 3 5% 7% 69%	1800
	21st to end	Day	4 5% 2 3 3 3 3 3 4 5% 64%	1800
December	1st to 10th	Day	1 3 1 2 2 1 2 2 3 6% 76%	2731
	11th to 20th	Day	2 3 1 4 4 3 3 2 4 7% 66%	3026
	21st to end	Day	2 4 1 3 2 2 3 2 4 6% 70%	4004
January	1st to 10th	Night	1 5% 3 7% 4 4 3 3 4 6% 60%	6079
	11th to 20th	Night	2 3 2 4 3 4 3 2 4 4 69%	5880
	21st to end	Night	2 4 2 6% 3 3 4 3 5% 7% 60%	6468
February	1st to 10th	Night	2 7% 2 5% 2 3 3 2 4 7% 63%	2540
	11th to 20th	Night	3 6% 2 4 3 4 4 3 4 7% 61%	2338
	21st to end	Night	3 6% 2 3 2 3 3 3 4 6% 64%	1980
March	1st to 10th	Night	2 4 2 4 3 3 4 3 4 6% 66%	5212
	11th to 20th	Night	5% 6% 3 6% 3 4 3 3 4 5% 59%	5000
	21st to end	Night	2 4 1 4 3 3 4 3 4 6% 67%	5242
April	1st to 10th	Night	3 4 1 3 3 2 3 3 6% 7% 65%	2000
	11th to 20th	Night	3 5% 1 4 3 3 4 2 4 6% 64%	1977
	21st to end	Night	3 3 1 4 3 3 3 3 5% 5% 67%	1955
May	1st to 10th	Night	3 5% 1 3 3 3 3 3 5% 6% 64%	3170
	11th to 20th	Night	6% 5% 2 5% 5% 4 5% 4 6% 7% 52%	2941
	21st to end	Night	4 2 1 3 3 2 3 2 3 5% 73%	2762
June	1st to 10th	Night	2 4 1 4 5% 5% 5% 5% 7% 8% 55%	1520
	11th to 20th	Night	3 3 1 3 3 3 4 3 4 8% 66%	1520
	21st to end	Night	5% 5% 1 5% 4 5% 5% 5% 6% 8% 50%	1520
July	1st to 10th	Night	5% 5% 2 7% 5% 5% 5% 5% 6% 7% 48%	2540
	11th to 20th	Night	3 3 1 5% 4 5% 7% 5% 10% 14% 44%	2817
	21st to end	Night	6% 5% 2 5% 4 5% 6% 5% 9% 11% 43%	3109
August	1st to 10th	Night	3 4 2 8% 7% 7% 8% 6% 8% 12% 34%	2996
	11th to 20th	Night	3 3 1 5% 5% 6% 6% 6% 8% 11% 46%	3113
	21st to end	Night	3 4 2 8% 6% 7% 8% 7% 10% 12% 34%	3487
September	1st to 10th	Night	5% 3 1 4 4 3 5% 4 9% 9% 53%	1900
	11th to 20th	Night	6% 3 2 5% 4 4 4 3 5% 7% 56%	1900
	21st to end	Night	4 2 1 4 3 3 4 3 4 6% 64%	2092
October	1st to 10th	Night	5% 3 1 2 2 2 2 2 3 4 74%	3800
	11th to 20th	Night	8% 4 2 4 2 3 3 2 4 6% 63%	3778
	21st to end	Night	3 2 1 2 1 2 1 2 4 5% 77%	4120
November	1st to 10th	Night	3 2 1 3 2 2 3 3 4 6% 72%	2416
	11th to 20th	Night	1 2 1 2 2 2 3 3 4 6% 73%	2600
	21st to end	Night	5% 5% 1 3 3 3 3 3 4 6% 64%	2600
December	1st to 10th	Night	2 2 1 3 2 2 2 2 3 7% 74%	4457
	11th to 20th	Night	2 3 1 3 3 3 3 3 5% 8% 67%	5181
	21st to end	Night	3 4 2 4 3 2 3 2 4 5% 68%	6974

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	23% 4 7% 25% 32% 9%	3915
	11th to 20th	Day	15% 5% 9% 25% 26% 21%	4100
	21st to end	Day	22% 5% 8% 15% 33% 15%	4510
February	1st to 10th	Day	23% 5% 10% 21% 28% 13%	1857
	11th to 20th	Day	21% 5% 8% 26% 25% 14%	1959
	21st to end	Day	21% 3 6% 18% 33% 20%	1650
March	1st to 10th	Day	18% 2 6% 13% 35% 25%	4654
	11th to 20th	Day	23% 4 11% 19% 29% 13%	5000
	21st to end	Day	17% 4 8% 28% 35% 7%	5720
April	1st to 10th	Day	19% 5% 8% 21% 31% 16%	2400
	11th to 20th	Day	22% 5% 6% 19% 29% 19%	2374
	21st to end	Day	19% 4 9% 22% 33% 13%	2341
May	1st to 10th	Day	14% 5% 9% 16% 33% 23%	3800
	11th to 20th	Day	23% 5% 10% 19% 29% 14%	3963
	21st to end	Day	11% 4 8% 13% 23% 42%	4825
June	1st to 10th	Day	17% 7% 13% 20% 24% 18%	2660
	11th to 20th	Day	16% 4 8% 13% 23% 36%	2660
	21st to end	Day	26% 6% 12% 18% 20% 17%	2660
July	1st to 10th	Day	25% 10% 13% 16% 16% 20%	4361
	11th to 20th	Day	30% 12% 20% 26% 8% 4	4077
	21st to end	Day	35% 12% 18% 24% 8% 3	4314
August	1st to 10th	Day	32% 12% 20% 18% 12% 5%	3925
	11th to 20th	Day	22% 8% 12% 28% 19% 11%	3762
	21st to end	Day	33% 10% 17% 22% 16% 2	4179
September	1st to 10th	Day	30% 7% 12% 20% 21% 9%	2280
	11th to 20th	Day	25% 6% 11% 19% 23% 16%	2280
	21st to end	Day	17% 4 8% 22% 33% 15%	2083
October	1st to 10th	Day	17% 3 5% 15% 30% 29%	3170
	11th to 20th	Day	24% 3 6% 15% 30% 22%	3150
	21st to end	Day	12% 1 5% 14% 42% 25%	3438
November	1st to 10th	Day	14% 3 8% 18% 41% 17%	1859
	11th to 20th	Day	14% 4 8% 23% 37% 14%	1800
	21st to end	Day	21% 4 7% 18% 30% 20%	1800
December	1st to 10th	Day	11% 3 7% 22% 41% 16%	2731
	11th to 20th	Day	18% 4 7% 22% 39% 11%	3024
	21st to end	Day	16% 2 8% 25% 36% 13%	4004
January	1st to 10th	Night	23% 5% 7% 22% 30% 13%	6079
	11th to 20th	Night	17% 5% 8% 23% 28% 19%	5880
	21st to end	Night	21% 6% 9% 17% 32% 15%	6468
February	1st to 10th	Night	22% 4 10% 22% 27% 15%	2540
	11th to 20th	Night	24% 3 10% 24% 25% 14%	2338
	21st to end	Night	20% 4 5% 17% 32% 22%	1980
March	1st to 10th	Night	18% 3 7% 12% 36% 25%	5212
	11th to 20th	Night	25% 5% 8% 16% 32% 14%	5000
	21st to end	Night	15% 4 8% 27% 36% 9%	5242
April	1st to 10th	Night	18% 5% 8% 21% 30% 18%	2000
	11th to 20th	Night	21% 5% 8% 18% 27% 21%	1977
	21st to end	Night	18% 6% 10% 21% 34% 12%	1955
May	1st to 10th	Night	16% 8% 10% 12% 28% 26%	3170
	11th to 20th	Night	25% 9% 14% 22% 17% 13%	2942
	21st to end	Night	12% 6% 9% 12% 18% 43%	2762
June	1st to 10th	Night	22% 9% 14% 18% 18% 18%	1520
	11th to 20th	Night	16% 4 7% 15% 21% 36%	1520
	21st to end	Night	28% 7% 14% 16% 16% 18%	1520
July	1st to 10th	Night	32% 9% 12% 16% 14% 18%	2500
	11th to 20th	Night	24% 11% 24% 30% 7% 4	2765
	21st to end	Night	30% 11% 20% 28% 10% 1	3011
August	1st to 10th	Night	38% 12% 18% 16% 11% 5%	2987
	11th to 20th	Night	27% 11% 16% 20% 18% 8%	3143
	21st to end	Night	35% 11% 18% 24% 9% 3	3487
September	1st to 10th	Night	24% 9% 18% 23% 19% 8%	1900
	11th to 20th	Night	25% 8% 13% 15% 24% 16%	1900
	21st to end	Night	19% 5% 10% 20% 31% 15%	2092
October	1st to 10th	Night	16% 3 6% 15% 35% 25%	3800
	11th to 20th	Night	23% 4 6% 14% 28% 25%	3778
	21st to end	Night	11% 2 5% 18% 38% 26%	4120
November	1st to 10th	Night	13% 2 6% 23% 37% 18%	2416
	11th to 20th	Night	12% 3 9% 22% 38% 16%	2600
	21st to end	Night	22% 4 6% 19% 30% 19%	2600
December	1st to 10th	Night	13% 3 6% 28% 34% 17%	4457
	11th to 20th	Night	15% 3 8% 20% 38% 16%	5182
	21st to end	Night	17% 4 8% 23% 37% 12%	6974

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	16% 29% 32% 18% 5%	300
	11th to 20th	Day	19% 29% 30% 16% 5% 1	300
	21st to end	Day	6% 29% 35% 19% 9% 1	330
February	1st to 10th	Day	14% 35% 31% 17% 3	300
	11th to 20th	Day	13% 39% 30% 15% 2	300
	21st to end	Day	21% 40% 26% 12% 1	249
March	1st to 10th	Day	14% 34% 33% 17% 2	363
	11th to 20th	Day	22% 30% 30% 14% 3 1	500
	21st to end	Day	22% 35% 30% 11% 2 1	550
April	1st to 10th	Day	16% 34% 36% 11% 3	500
	11th to 20th	Day	17% 39% 31% 11% 2	492
	21st to end	Day	14% 32% 42% 10% 2	481
May	1st to 10th	Day	11% 33% 40% 13% 2 1	463
	11th to 20th	Day	11% 17% 39% 25% 8% 1	567
	21st to end	Day	8% 18% 38% 28% 7% 1	734
June	1st to 10th	Day	3 8% 32% 38% 18% 2	680
	11th to 20th	Day	6% 12% 30% 34% 16% 1	680
	21st to end	Day	7% 9% 27% 35% 19% 4	680
July	1st to 10th	Day	5% 2 24% 34% 29% 6%	671
	11th to 20th	Day	4 2 10% 43% 33% 8%	507
	21st to end	Day	6% 1 11% 40% 33% 9%	531
August	1st to 10th	Day	4 3 17% 44% 26% 5%	487
	11th to 20th	Day	5% 3 24% 40% 23% 5%	477
	21st to end	Day	4 3 22% 44% 22% 5%	539
September	1st to 10th	Day	7% 4 26% 41% 20% 3	490
	11th to 20th	Day	6% 6% 36% 36% 13% 3	490
	21st to end	Day	5% 12% 34% 30% 15% 5%	300
October	1st to 10th	Day	10% 19% 29% 25% 13% 3	300
	11th to 20th	Day	11% 20% 33% 23% 9% 3	300
	21st to end	Day	13% 21% 33% 22% 9% 2	330
November	1st to 10th	Day	12% 31% 34% 16% 6%	300
	11th to 20th	Day	8% 22% 38% 23% 7% 1	300
	21st to end	Day	16% 28% 30% 19% 8%	300
December	1st to 10th	Day	14% 28% 30% 20% 8%	300
	11th to 20th	Day	11% 32% 34% 19% 4	300
	21st to end	Day	19% 34% 29% 14% 4	330
January	1st to 10th	Night	5% 21% 36% 26% 11% 1	895
	11th to 20th	Night	8% 17% 39% 26% 8% 2	800
	21st to end	Night	5% 18% 40% 26% 10% 1	880
February	1st to 10th	Night	6% 20% 44% 24% 5% 1	800
	11th to 20th	Night	8% 25% 40% 22% 5%	784
	21st to end	Night	10% 23% 48% 18% 2	660
March	1st to 10th	Night	8% 23% 38% 26% 5% 1	800
	11th to 20th	Night	10% 18% 33% 31% 9%	800
	21st to end	Night	8% 19% 43% 25% 4	775
April	1st to 10th	Night	8% 23% 42% 23% 4	600
	11th to 20th	Night	9% 23% 34% 28% 6%	593
	21st to end	Night	6% 19% 41% 28% 5%	587
May	1st to 10th	Night	5% 14% 41% 30% 9%	570
	11th to 20th	Night	7% 10% 33% 34% 15% 1	561
	21st to end	Night	6% 13% 34% 38% 9% 1	617
June	1st to 10th	Night	3 6% 28% 44% 19%	570
	11th to 20th	Night	2 7% 32% 43% 15% 1	570
	21st to end	Night	6% 5% 20% 43% 25% 2	570
July	1st to 10th	Night	5% 1 13% 43% 34% 4	555
	11th to 20th	Night	3 1 7% 38% 45% 5%	552
	21st to end	Night	5% 2 6% 32% 48% 6%	624
August	1st to 10th	Night	5% 1 9% 32% 44% 8%	567
	11th to 20th	Night	4 2 13% 41% 37% 4	564
	21st to end	Night	4 1 10% 44% 35% 6%	627
September	1st to 10th	Night	5% 2 13% 47% 29% 4	570
	11th to 20th	Night	6% 3 16% 47% 26% 2	570
	21st to end	Night	5% 6% 24% 43% 20% 2	574
October	1st to 10th	Night	8% 8% 23% 41% 19% 1	760
	11th to 20th	Night	6% 10% 34% 35% 13% 3	760
	21st to end	Night	6% 13% 31% 32% 14% 4	836
November	1st to 10th	Night	4 13% 36% 32% 13% 2	856
	11th to 20th	Night	3 16% 37% 32% 10% 2	1000
	21st to end	Night	9% 17% 34% 28% 11% 2	1000
December	1st to 10th	Night	8% 19% 37% 27% 7% 1	1000
	11th to 20th	Night	7% 21% 38% 26% 8%	1000
	21st to end	Night	11% 21% 42% 22% 4	1100

Page generated at 2025-04-23 07:25:05. Version ac07

Copyright © 2025 Attilla Danko.